Numerous diseases and conditions of the circulatory system and other organs of the body are beneficially treated by the occlusion of blood vessels. Arteriovenous fistulas, arteriovenous malformations, aneurysms and pseudoaneurysms, patent ductus arteriosus, gastrointestinal bleeding, renal and pelvic bleeding, and tumors are examples of the numerous maladies that can be treated by blocking associated blood vessels. Placement of various substances within the blood vessels is one of the methods of encouraging the formation of thrombus (clot) which leads to the complete occlusion of the blood vessels. As early as 1975, coils were successfully used to occlude the renal arteries. Gianturco, et al., Mechanical Devices for Arterial Occlusions, 124 Am. J. Roent. 428 (1975). The purpose of the coil is to encourage quick formation of a thrombus (a blood clot) around the coil. The coils are currently in use for a wide range of treatments, and are referred to variously as occlusive coils, embolization coils, or Gianturco coils. They are commercially available from Cook, Inc. and Target Therapeutics, Inc.
Of the many diseases that may be treated with embolic coils, aneurysms are of particular interest. Embolization coils of appropriate size for placement within aneurysms are commercially available from Target Therapeutics, Inc. Embolization coils made with electrolytic mechanisms for detachment from the delivery catheter are referred to as GDC's or Guglielmi Detachable Coils. The use of GDC's is illustrated, for example, in Klein, et al., Extracranial Aneurysms and Arteriovenous Fistula: Embolization with the Guglielmi Detachable Coil, 201 Radiology 489 (1996). Use of the GDC coils within the brain is illustrated, for example, in Casasco, et al., Selective Endovascular Treatment Of 71 Intracranial Aneurysms With Platinum Coils, 79 J. Neurosurgery 3 (1993).
Because Gianturco and Guglielmi coils are often used to occlude aneurysms in critical areas of the body, it is important that they remain in place where they are implanted. However, migration of the coils after placement is a common but dangerous problem encountered with these coils. Watanabe, Retrieval Of A Migrated Detachable Coil, 35 Neuro. Med. Clin. 247 (1995) reports the migration of a coil from a placement in the superior cerebellar artery into the basilar artery. Halbach, et al., Transarterial Platinum Coil Embolization Of Carotid Cavernous Fistulas, 12 AJNR 429 (1991) reports the migration of a coil from the internal carotid artery. Migration is particularly common with coils placed in wide neck aneurysms. The possible migration of coils is a danger that must be considered in every procedure, and actual migration can be a life threatening complication, since embolization at an unwanted site could occlude a critical blood flow. Migration of the coil may also represent a failure of the intended therapeutic procedure.